Now that Lightroom has gone subscription only, no longer offering a stand alone, many people are looking for alternatives again.
So far, I find AlienSkin Exposure 3, On1 Photo Raw, and Topaz Studio to be the strongest contenders. Exposure 3 and On1 have a feature that Topaz doesn’t at this time. The ability to have different versions, virtual copies, of the same image, with different edits, without filling your HDD with multiple image files.
On1 had more tools/Effects than AlienSkin, but AlienSkin works faster on older computers, or with machine with only 16gb of memory.
All three have plugins that work with CS6 (there is a way to get them to work with CS5. Download trial version of Photoshop CC, install On1/Alienskin/Topaz, and then copy/paste the plugins from the CC plugin folder to CS5 plugin folder. If you get any error message about a specific DLL missing, copy it from the Photoshop CC directory into the CS5 directory. Nothing says you have to uninstall the CC trial version, so leave it there to install updates)
My personal favorite is On1 Photo Raw, followed very closely by AlienSkin Exposure 3. I do like editing my RAW photos with these two, and then in Photoshop, using the Topaz Studio/Labs plugs to add extras.